The invention concerns a method for the optical recognition of alphanumeric characters.
The optical recognition of alphanumeric characters, usually termed optical character recognition (OCR), is used to automatically convert written, printed or, if desired, even handwritten texts into a data form that can be electronically processed. The characters being recognized are optically scanned and binarized to create a file that can be analyzed with suitable software and transformed into a computer-compatible data record.
Various techniques are known for using so-called OCR characters, particularly standardized characters, to facilitate a comparison with reference characters stored in a memory.
In so-called pattern matching, a character pattern detected by optical scanning is compared against stored reference characters by pattern overlay for determining the best possible match. This method is problematical when different fonts, character sizes and/or degrees of character definition need to be recognized.
In the so-called feature recognition technique, the characters are assigned certain characteristic features, such as vertical and horizontal strokes, crossing points and curves. The characters to be recognized are examined with regard to such features and compared against pattern forms stored in memory. This technique is less dependent on type of font and/or size and is therefore more reliable.
In so-called angular section analysis, the character or mark to be recognized is cut at different angles by a family of straight lines. The number of black contrast points on the individual lines and the number of intersection points of the lines with the character or mark being scanned are analyzed and compared by a computer against memorized reference characters.
These known techniques depend heavily on standardized fonts, or approximations thereof, for recognizing the characters or marks.